1. Field of the Invention
This invention relates to an apparatus for detecting ophthalmic diseases in a patient's eye, and more particularly to an apparatus for detecting ophthalmic diseases in which laser light is radiated via an optical system at one spot in the camera oculi of the patient's eye, particularly in the anterior chamber thereof and the laser light scattered therefrom is analyzed to measure the protein concentration for ophthalmic disease detection in the camera oculi.
2. Description of the Prior Art
The camera oculi is comprised of the camera oculi anterior (anterior chamber) and the camera oculi posterior (posterior chamber). The camera oculi anterior is defined by a space surrounded by the rear surface of the cornea, a part of ciliary body, iris, and the front surface of the crystalline lens, while the camera oculi posterior is defined by a space surrounded by the rear surface of the iris, inner surface of the ciliary body, and front surface of the crystalline lens. The camera oculi is filled with transparent humor aqueous, which has chemical and physical characteristics different from lymphatic liquid and has a close relation with the metabolism of the cornea or crystalline lens. The humor aqueous contains proteins which increase causing the camera oculi to be turbid when it becomes inflamed.
In this respect, the measurement of protein concentration in the camera oculi of the patient's eye is of great importance in determining whether the camera oculi is inflamed, that is, whether a blood-aqueous barrier functions normally or not.
To measure the protein concentration in the camera oculi, a slit lamp microscope is very often used to determine the turbidity by grading via naked eyes. This is, however, disadvantageous because the judgment depends upon the person who performs the measurement.
On the other hand, a photographic measuring method has been developed to make a quantitative measurement of the protein concentration. This method is, however, too complicated to analyze, thus very difficult to apply in a clinical examination.
To overcome this problem, an apparatus for detecting the ophthalmic diseases has been proposed which includes means for focusing a laser beam at a selected spot in the camera oculi of an eye. In the apparatus, the light scattered from the eye is photoelectrically detected and converted into an electrical signal which is subsequently used to determine the protein concentration essential to ophthalmic disease detection in the camera oculi of the patient's eye. See, for example, Japanese Patent Laying-open No. 120834/87.
This apparatus, however, has also the drawback that the light reflected or scattered at the cornea, iris, lens or artificial lens after an operation to remove cataracts impinges on the spot to be measured in the anterior chamber or intrudes into the laser scattered light in the form of noise. This disadvantageously makes the measurement inaccurate and the measured value poorly repeatable. This problem is further exacerbated by a varying intensity of the laser beam produced from the laser source due to fluctuating energy power or because a photodetector for receiving the scattered light changes in its sensitivity.
The apparatus has further such a drawback that the high intensity of laser light burdens the patients during a measurement.